Four-stroke engines are increasingly preferred for use in outboard marine drives with the aim of reducing emission to keep the environment pollution-free. However, four-stroke engines require lubricating oil stored in an oil pan at a proper level for their operation, and it is therefore necessary to provide means for inspecting the level of lubricating oil. In small four-stroke engines typically used for portable power generators and lawnmowers, the oil level is inspected by -using an oil gauge rod or a dip stick which is passed into an oil filler tube extending upward from an oil pan. Draining of lubricating oil is typically accomplished by tilting the engine, and letting the lubricating oil flow out of the oil filler tube (refer to Japanese UM laid-open (kokai) publication No. 1-83117).
This approach however is not suited for outboard marine drive engines because the outboard marine drives have relatively large lengths and cannot be readily detached from the boat. Therefore, there has been a need to provide a convenient arrangement for managing lubricating oil for small outboard marine drive engines which is simple but convenient to use.